Sealed beam lamps are ubiquitous and used in a variety of lighting applications. They are employed, for example, as automobile headlights, theatrical lights, outdoor architectural lights, aircraft landing lights, and spot lights. A “sealed beam” lamp is a type of lamp that includes a reflector and filament manufactured as a single assembly, over which a front cover or lens, usually of clear glass, is permanently attached. Popular sizes of sealed beam lamps are the PAR56, PAR38, and PAR30, where the “PAR” is an acronym for Parabolic Aluminum Reflector. The PAR has come to be accepted as a non-SI unit of measurement equal to one-eighth of an inch. For example, a PAR38 light bulb is a light bulb having a diameter equal to 4.75 inches. Common light beam spreads for sealed beam lamps are flood, spot, narrow spot, or very narrow spot beams.
Spot lights are found in various retail, residential, and architectural settings everyday. For example, virtually all supermarkets, convenience stores, drug stores, department stores, jewelry stores, discount stores, motor vehicle dealers, and specialty apparel stores use spot lighting. Conventional light sources typically employed in spot lighting applications, however, suffer from a number of drawbacks.
In particular, fluorescent light sources, although often efficient and inexpensive, are too diffuse to be effective for spot lighting. In other words, these sources are poorly suited for applications requiring directed light. In addition to poor light output distribution, color temperatures of these sources are not well-suited for many applications. Further, although halogen lamps tend to have low upfront costs, good color rendition and good beam control, they are typically quite inefficient for spot light applications, having light output efficiencies in the range of just 10-20 lumens/watt. Another type of lamp typically used for spot lighting is the ceramic metal halide (“CMH”) lamp. While CMH lamps can offer good beam control and energy efficiency, they typically have high initial costs and can be too bright and non-dimmable, making adjacent areas often look dark by comparison. Finally, traditional incandescent lighting tends to be too inefficient for spot lighting applications.
Given the widespread use of spot lighting and other types of lighting in general, vast energy savings for the benefit of both business and consumer users and the environment could be realized if the energy efficiency of lighting could be improved without compromising performance. Despite these potential energy savings and the growing environmental concerns that have existed for years in the world, however, there still exists a need for a sealed beam lamp having substantially improved energy efficiency. In particular, there exists a need for a highly-efficient, durable and relatively inexpensive spot light capable of providing aesthetically pleasing illumination with a uniform beam pattern to fit application and end-user expectations.
The advent of digital lighting technologies, i.e., illumination based on semiconductor light sources, such as light-emitting diodes (LEDs), offers a viable alternative to traditional fluorescent, HID, and incandescent lamps. Functional advantages and benefits of LEDs include high energy conversion and optical efficiency, robustness, lower operating costs, and many others. The LEDs' smaller size, long operating life, low energy consumption, and durability make them a great choice in a variety of lighting applications.
Accordingly, it would be desirable to provide an improved luminaire employing LED light sources, addressing the drawbacks of conventional technologies, while providing quality illumination. Besides the required high color rendering properties, quality-of-light considerations include several other observable and measurable criteria like useful and applicable spatial distribution of the illumination, and a white emission of desired color temperature with no “halos” or other texture and color artifacts. It is also desirable for this luminaire to retain commonly encountered form factors, so that existing hardware, sockets, and power connections could be employed, thereby further reducing costs and reducing waste associated with retooling, and facilitating adoption of the improved luminaire.